Acta Medica Okayama 70 1 2004 Thermodynamics of a two-dimensional Yukawa fluid EN Hiroo Totsuji M. Sanusi Liman Chieko Totsuji Kenji Tsuruta <p>Thermodynamic quantities of a two-dimensional Yukawa system, a model for various systems including single-layered dust particles observed in dusty plasmas, are obtained and expressed by simple interpolation formulas. In the domain of weak coupling, the analytical method based on the cluster expansion is applied and, in the domain of intermediate and strong coupling, numerical simulations are performed. Due to reduced dimensionality, the treatment based on the mean field fails at the short range and exact behavior of the binary correlation is to be taken into account even in the case of weak coupling.</p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 70 1 2004 Folding of the triangular lattice in a discrete three-dimensional space: density-matrix renormalization-group study EN Yoshihiro Nishiyama <p>Folding of the triangular lattice in a discrete three-dimensional space is investigated numerically. Such "discrete folding" has come about through theoretical investigation, since Bowick and co-workers introduced it as a simplified model for the crumpling of the phantom polymerized membranes. So far, it has been analyzed with the hexagon approximation of the cluster variation method (CVM). However, the possible systematic error of the approximation was not fully estimated; in fact, it has been known that the transfer-matrix calculation is limited in the tractable strip widths Lless than or equal to6. Aiming to surmount this limitation, we utilized the density-matrix renormalization group. Thereby, we succeeded in treating strip widths up to L=29 which admit reliable extrapolations to the thermodynamic limit. Our data indicate an onset of a discontinuous crumpling transition with the latent heat substantially larger than the CVM estimate. It is even larger than the latent heat of the planar (two-dimensional) folding, as first noticed by the preceding CVM study. That is, contrary to our naive expectation, the discontinuous character of the transition is even promoted by the enlargement of the embedding-space dimensions. We also calculated the folding entropy, which appears to lie within the best analytical bound obtained previously via combinatorics arguments.</p> No potential conflict of interest relevant to this article was reported.